It is a striking statistic – and, for many theatre dramatists, a depressing one – that a third to a half of the shows in the London West End in recent years have tended to be based on material best known as films: recent arrivals include Strangers on a Train, From Here to Eternity and The Commitments. Although in all those cases the pieces began as a novel, it was a film that made the product bankable, and the stage versions have a cinematic texture.

This rush from page to stage has financial and technological explanations, but may also prove short-lived because the history of drama shows that literature and theatre have frequently made fractious companions.

The consummation, though, has often been attempted. In the 19th century, producers were rapidly alert to the dramatic possibilities of the characters and narratives of Charles Dickens, who, as Claire Tomalin's biography suggests, turned to writing after being frustrated in his hope of a theatre career. Some of his stories, including The Pickwick Papers, were on stage before their serial publication was even complete, with impatient playwrights sometimes finishing off the plots. Such presumption – and the fact that the plays were generally unauthorised and so of no financial benefit – not surprisingly, irritated Dickens.

But the inherent theatricality of his work has meant that his books have often been an inspiration to impresarios. Two Dickensian stagings at the end of the 1970s have remained hugely influential: the RSC's The Life and Adventures of Nicholas Nickleby (1980), adapted by David Edgar and directed by Trevor Nunn and John Caird, and a version of Bleak House created by Mike Alfreds in 1977 as one of the earliest projects of the touring company, Shared Experience. That outfit – under later artistic directors, such as Polly Teale – has remained a leader in turning reading into theatre, with dramatisations of classics including The Mill on the Floss, Anna Karenina and War and Peace. The two Tolstoy novels were also adapted by Robert David Macdonald (who died in 2004), a pioneering adapter at the Glasgow Citizens theatre, who impressively filleted Proust's A la Recherche du Temps Perdu into a single play called A Waste of Time.

All of these staged Bookers have happened in the last 10 years, which is surely not coincidental. The most successful recent literary adaptations in theatre – including War Horse and The Curious Incident of the Dog in the Night-Time and the musical version of Roald Dahl's Matilda – would have been impossible a decade ago, at least in such a visually fluent and enthralling form. However, though modern methods of design, lighting and scene-changing have been advantageous to greasepaint literature, it remains a problem that satisfying novels rarely prove an easy fit for theatre. Ever since Edgar, Nunn and Caird concluded that Nicholas Nickleby was voluminous enough to spawn two separate evenings of more than four hours each, theatricalised novels have tended to stretch to the length of at least two Shakespeare plays: His Dark Materials at the National Theatre (in a 2003 version by Nicholas Wright before the film) became two long evenings, as have the Mantel novels, while the current Middlemarch, dramatised by the actor Geoffrey Beevers, consists of three separate dramas – Dorothea's Story, The Doctor's Story and Fred and Mary – which, on Saturdays, are performed successively in the morning, afternoon and evening.

Yet, even in multi-play adaptations, the constant squashing of content is apparent to anyone who has read the book closely. This is one reason why films have been a more natural source for stagings because transferring two and a bit hours in one dark room to the same amount of time in another is less daunting.

But the mistake – on either side of the footlights – is to think that the show is a walking-and-talking book. The premier modern theatrical translator-adapter Mike Poulton, whose work included Morte D'Arthur and The Canterbury Tales before taking on the Mantels for the RSC, warns in the preface to the published texts of the Cromwell plays: "It might be thought that the sheer length of the two books [1,007 pages] might present problems. I never thought so. The way a novel is structured cannot be reproduced on the stage … they had to be completely reimagined as plays."

Central to this rethinking is viewpoint or narration. The RSC's Nicholas Nickleby innovatively distributed the linking prose among the cast; an approach that had the advantage of sometimes allowing characters to deliver description or thoughts relating to themselves, reflecting the blurred exterior/interior perspective that is one of the signature devices of novels.

In the case of Wolf Hall and Bring Up the Bodies, the situation is complicated because, although every scene is refracted through the consciousness of Cromwell, the reader is not quite in his head but, in effect, behind him: Mantel has used the metaphor of a hovering camera. As a novelist, she can keep us focused on Cromwell; but, as a theatre audience, we can look wherever we want among the busy throng on stage.

Poulton's solution – in scripts on which he worked very closely with the novelist – is completely to avoid direct address from Cromwell to the audience and to employ two characters, Rafe Sadler from Cromwell's house and Thomas Wyatt from King Henry's court, as "confidants" with whom he can discuss matters that, in the books, are only thought or inferred. Poulton has also introduced a series of ghostly presences – including the spectre of Cardinal Wolsey – who vocalise and physicalise reflections that, in the books, occur only in memory.

The major loss for a novelist in the theatre is control – especially of characterisation. In a book, an incidental figure makes exactly the impact that the author permits them, but, in theatre, the casting of a brilliant young actor in a small role or an under-powered performer in a larger one can significantly change the balance of the narrative. Notoriously, the biggest burden for any author whose work is dramatised (for either stage or screen) is the complaints that A or B doesn't look at all how a certain reader imagined them. Most critics and bloggers agree that Ben Miles, who plays Cromwell for the RSC, embodies the brilliant but haunted political fixer written by Mantel, but Miles's version will be challenged by Mark Rylance's in the forthcoming BBC TV series based on the books.

Fiona Shaw, in the staging of Tóibín's The Testament of Mary, had the particular challenge of embodying a figure whom scripture and art have turned into a blur of desexualised perfection: the mother of Christ. British audiences this spring may become less fixated on whether the Virgin Mary would have been so earthy or sounded Irish, but such reactions are an example of the advantage to novelists of their characters being unseen and unheard.

In another sense, though, Tóibín's book was a natural for the stage (and started life as a play called Testament in 2011): its first-person narrative easily becomes a dramatic monologue. The novelist scripted it himself, which may have been a brave move because one of Tóibín's most successful novels – The Master – dramatises the life of a novelist, Henry James, whose attempts to become a playwright were literally booed off the stage.

Although the lure of live drama to fiction writers is shown by the fact that David Lodge - whose novel Author, Author also depicts James's humiliation as a dramatist - has written two original plays as well as turning one of his novels, Thinks, into a play called Secret Thoughts.

It would be interesting to ask the audiences at Stratford, just before the lights go down on the Mantel adaptations, how many of them have read the books. We would expect a high percentage because one of the attractions of novels to theatre producers is – as with films brought to stage – the instant familiarity of the material: the advertising finds a willing target. Unusually, the printed playscripts are jointly produced by the theatrical publisher Nick Hern Books and 4th Estate, who put out the original books, with the cover incorporating details from the jackets of Wolf Hall and Bring Up the Bodies.

Those who read the Poulton volume as well as the Mantel novels will receive a fascinating education in the necessarily different strategies of plays and novels. In the book of Bring Up the Bodies, for example, the first encounter between Cromwell and Anne Boleyn, in which they joust for power while discussing her unborn child, runs to six pages, in which we know the internal thoughts and distractions (other business) of him, but only the external reactions of her: blushes, scowls, sighs. In the Poulton version, this becomes a conversation of just over a page. Certain lines of dialogue transfer intact, including Anne's "Make terms with me before my son is born" and "Those who are made can be unmade." But, whereas Mantel has Cromwell replying "I entirely agree" to the latter warning, Poulton gives her: "They can. I know it, Madam."

The greater formality of the spoken dialogue reflects both a stage dramatist having to think deeply about the exact tones in which a queen and a courtier might converse and also – because the stage lines end the scene, whereas in the novel it continues – to convey a greater whack of finality, although both sets of words carry the ambiguity that both speakers believe they have the power to unmake the other. It is, though, for the actor playing Anne – Lydia Leonard – to decide whether she wishes to redden or exhale where Mantel specified and, if she chooses, she can vary the decisions night by night.

These are small examples of how – for good or ill – a book escapes its author on the stage. A novel is a dictatorship, but a dramatisation is a democracy.